articles+ search results

активный ил, сточные воды, инкубирование, очистные сооружения молочного производства, Chemical engineering, and TP155-156

Гранулы активного ила получены инкубированием в аэробных условиях активного ила, отобранного на очистных сооружениях молочного производства, на сточных водах данного производства. Изучена динамика снятия загрязнений (по показателю ХПК) в сточных водах молочного производства свежесформированными гранулами в сравнении с флоккулированным активным илом.

r32, flow boiling, heat transfer coefficient, pressure drop, new correlation, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

The objective of this study is to establish generalized correlations for R32 flow boiling heat transfer and frictional pressure drop in channels with wide ranges of geometric and flow parameters. In this paper, two consolidated databases for heat transfer and frictional pressure drop were amassed from open literature, which involved R32 as working fluid. The heat transfer database consisted of 1 489 data points from 8 sources, with hydraulic diameters of 1—6.3 mm, while the pressure drop database included 496 data points from 8 sources, which covered hydraulic diameters of 0.643—6 mm. A new heat transfer coefficient correlation and a frictional pressure drop correlation were developed based on the prediction technique of dimensionless parameter analysis considering the governing force effect. Moreover, the existing correlations were also introduced to perform assessment. The validation results show that the existing correlations have poor results of mean absolute errors (MAE) and significantly high maximum absolute errors (MAX), but the new heat transfer coefficient correlation provides a superior prediction accuracy with a MAE of 14.59% and 90.85% of data within ±30% error bands. In addition, the new pressure drop correlation exhibits the best performance, which yields a MAE of 17.86%. The two new correlations have a broad application range and satisfactory prediction accuracy, which are applicable to analyze the heat transfer and pressure drop performance of heat exchangers with refrigerant R32.

thermal contact resistance (tcr), cryogenic, cryocooler, brass, lamination method, measurement, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

Prior studies on cryogenic thermal contact resistance (TCR) measurement mainly focus on liquid nitrogen temperature region and above. There are limited solid TCR data in the lower temperature region. The present measurement is based on an RDK-408D2 two-stage G-M cryogenic refrigerator. By using the laminated method, the TCR data of brass samples in the temperature range of 10—30 K at different roughnesses and preloads are measured and the influence of different factors on TCR is discussed. The results show that the TCR of the brass contact surface in this temperature zone is between 6.89×10-4 and 1.86×10-2 m2·W/K. With a smaller roughness of the contact surface, higher temperature, and greater pre-tightening force, the TCR becomes smaller. This behavior is consistent with the conventional qualitative understanding. The above cryogenic experimental data can provide certain support for the calculation of TCR for related cryogenic application design.

solar energy, wastewater, diffusion, contactless evaporation, thermal resistance network, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

Zero-liquid discharge is an efficient pathway for high concentration brine and wastewater treatment. Contactless solar evaporation is a new configuration proposed in recent years towards this target, which has the advantages of solar energy utilization, simple structure, passive operation, and anti-fouling. Considering that contactless solar evaporation lacks an effective predictive model to guide the optimization in real scenarios, a steady-state thermal resistance network model is developed for the first time and further analyses are conducted. According to the results, two main heat sources of the water, radiative heat transfer and air gap heat transfer, contribute 54.2% and 45.8% to the total heat flow and both have a significant impact on the evaporation performance. The larger air gap thickness has a negative effect on both of the two heat transfer processes. The evaporation rate with an air gap thickness of 10 mm is only 70% of that with an air gap thickness of 4 mm. Additionally, decreasing vapor diffusion resistance is an efficient way to increase the evaporation rate. The evaporation rate triples when the vapor diffusion coefficient increases from 5×10-6 m2/s to 2.5×10-5 m2/s.

polar region, circular tube component, convective heat transfer, numerical simulation, experimental test, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

Electric heat tracing is often used for cold protection in polar ocean engineering equipment. Heat balance is the key problem of convective heat transfer. In this paper, the circular tube structure is taken as the research object. Numerical simulations using Fluent and model experiment are conducted to analyze the change of the convective heat transfer coefficient of the circular tube component under the polar environment with a wind speed range of 0—40 m/s and a temperature range of -40—0 ℃. Based on the numerical simulation data, the prediction model of the convective heat transfer coefficient of the electric heating tube is obtained. The results show that the convective heat transfer coefficient increases with the increase of wind speed and the decrease of temperature. When the temperature is below -30 ℃, or when the wind speed is greater than 25 m/s and the temperature is lower than -20 ℃, the influence of temperature on the convective heat transfer coefficient increases. The rationality of the model is verified by experimental test.

ship block transfer, block state identification, block transfer monitoring, hidden markov model (hmm), Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

Ship block transfer is important to the orderly flow of blocks between crafts, which is costly. Shipyard managers have to monitor the actual transfers, especially the unproductive transfers that occur when blocks are obstructed or reworked. A high-load shipyard, called S, often uses one site for multiple purposes, and the difficulties in obtaining the state of ship blocks through the time-site data of blocks provided by the existing monitoring technology make it difficult to monitor two types of unproductive transfers. To address this problem, four hidden Markov models whose parameters are calculated by a supervised approach are proposed, and a Viterbi algorithm based method is proposed to identify the state of blocks, achieving an accuracy of up to 93.5% on the test dataset. One of the hidden Markov models is applied to the time-site data of blocks to monitor two types of unproductive transfers in shipyards. Preliminary suggestions for improving the blocks transfer process based on monitoring results are proposed.

impinging jet, fin array, enhanced heat transfer, airfoil anti-icing, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

Impinging jet is widely implemented at the leading edge of aircraft wings for anti-/de-icing purposes. To further improve the anti-icing performance, this paper utilized numerical simulation to explore the impingement heat transfer characteristics of different fin arrays on flat plate and concave surface sequentially. The fin array in the flat-plate model consisted of 8, 12 straight fins or 12 curved fins. The concave surface model consisted of 8 short or long fins. The results show that the addition of fin arrays on the flat plate and airfoil surface can significantly improve the jet impact heat transfer performance at different Reynolds numbers. Compared with non-fins, the comprehensive heat transfer effect on the airfoil surface is increased by 4%—10%, especially for the stagnation region. Further flow field analysis reveals that adding fin array not only increases the area of heat transfer, but also strengthens the turbulent kinetic energy of impingement jet flow, leading to an enhancement of heat transfer performance.

formation control, backstepping method, movement state, state estimation, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

A multi-shift tooling coordinated operation control strategy based on the backstepping method is investigated, a desired motion state planning scheme based on the improved artificial potential field method and the pure trajectory tracking method is proposed, and the actual situation is determined according to the adaptive Monte Carlo positioning method. For the estimated value of the motion state, a queue controller in combination the anti-stepping method and the virtual pilot following method is designed. A simulation model based on the robot operation system (ROS) environment is constructed, and the simulation is verified. The results show that the proposed formation error calculation method can improve the accuracy of error estimation. The formation control strategy can make the formation error converge within 6.2 s, and the designed formation controller can meet the operation requirements of multi-shift tooling.

steam generator, level control, variable universe algorithm, fuzzy control, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

Aimed at the important position of the steam generator liquid level control system in maintaining the safe and efficient operation of the power plant in the PWR nuclear power plant, and the fact that there exist strong nonlinear characteristics in the controlled object of the steam generator liquid level under different load sections and changing conditions, this paper proposes a fuzzy control algorithm with the adaptive variable universe function. Based on the general fuzzy control algorithm, the Lyapunov function is constructed through the nonlinear system model, and the optimal adaptive expansion factor is solved based on the ideal control law, and Lyapunov theorem is used to prove the stability of the control system. The simulation results show that the fuzzy control with adaptive variable universe function can better effectively control the liquid level of the steam generator under different working conditions and variable working conditions than the traditional proportional integral (PI) control and fuzzy PI control. The problem of controller overrun is solved, and the system has a better robustness.

sequential prediction, mode decomposition, threshold denoising, clustering algorithm, auto regressive model, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

The changes in the status parameters of the thermal system reflect the operating status of the system in real time. The forecast results of the trend extraction and time series prediction of the current equipment status parameters can be used as a reference for the next operation management strategy and equipment maintenance, which can be used for the long-term system safe and stable operation. In this paper, a method which is described as MWSA, based on the midpoint and regression based empirical mode decomposition (MREMD), the wavelet threshold denoising (WTD) and midpoint and techniques, the singular value decomposition (SVD) and optimized parameter permutation entropy (PE), and an auto regressive integrated moving average model (ARIMA), is applied to the single-parameter time series prediction of thermal systems. First, the MREMD is used to decompose the monitored operating state parameters into a number of intrinsic mode functions (IMF) and residual components. Next, the components that do not meet the screening conditions are subjected to wavelet thresholding. The denoised components and the components that originally meet the filtering conditions are recomposed into new IMF components. Finally, the K-means clustering algorithm based on SVD and PE is used to classify the recomposed IMF components, the component with a lower entropy value is selected and reconstructed into a trend item, and ARIMA is used to predict. An actual case verifies that this method can effectively overcome the interference of high-frequency noise in the original parameter timing, and the prediction accuracy is higher than that of similar methods without noise reduction treatment.

automatic guided vehicle (agv), multi-trip, task allocation, path planning, time window algorithm, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

To realize efficient scheduling of automatic guided vehicles (AGV) in the aircraft final assembly workshop, a two-stage method of AGV task allocation and path planning is proposed which effectively solves the problem of multi-trip distribution scheduling of AGV in the workshop. In the task allocation stage, an AGV task allocation model based on the trip is established to improve task allocation efficiency. In the path planning stage, the time window algorithm is used to initialize, update, and arrange the time window of the resources occupied by the AGV. Considering that the latest delivery time constraints may be violated due to obstacle avoidance and waiting, three adjustment strategies are designed to realize the conflict-free path planning of AGV, including the package exchanging strategy, the priority exchanging strategy, and the reserved conflict duration relaxation strategy. In numerical experiments, the average solving time of the two-stage method applied to problems with the scale of 50, 100, and 150 is 15.86, 41.12, and 162.29 s, which indicates that the two-stage method effectively alleviates the complexity of the multi-trip AGV scheduling problem. The two-stage method can realize the scheduling of the AGV in aircraft assembly workshop within a reasonable time and adapt to the rapid increase in the annual production of aircraft.

integrated energy system, biogas generation, demand response, optimal sizing, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

There are abundant biomass resources in China’s rural areas, which can be converted into biogas energy through fermentation systems. However, the rewards of the investments of the pure biogas projects is poor because biogas is a cheap resource. This paper proposes a 100% renewable grid-connected wind-solar-biogas integrated energy system which utilizes the complementarity between solar energy, wind energy, and biogas to provide users with biogas and electricity. The battery-like characteristics of biogas are modeled based on the microbial fermentation kinetic model and the temperature-sensitive characteristics of biogas fermentation. In addition, the demand-side response is considered to further increase the flexibility of the system, and the time-of-use electricity price is used to save power purchase costs, thereby minimizing investment costs and annual operating costs. Case studies show that the wind-solar-biogas micro-energy network can effectively reduce the total investment cost by 3% to 9% while increasing the benefit by 1.27 to 2.40 times.

electric vehicles (evs), charging schedule, smart grid, random environment, renewable energy source, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

With the increasing scale of electric vehicles (EVs), the adaptive management of its charging behavior becomes an urgent problem to be solved. From the point of view of charging service provider, an online management algorithm for EV charging is proposed based on the Lyapunov optimization theory under the random environment in this paper, considering renewable sources energy, storage equipment, time-varying electricity price, and the tolerable delay of EV, with an aim of maximizing the benefits of charging service providers (i.e., minimizing the cost of electricity purchased). The performance of the proposed algorithm is analyzed to verify that it can achieve near-optimal optimization results without any a priori statistical information about the system inputs (renewable energy generation, charging demand, and time-varying electricity price). The simulation results show that the proposed algorithm can effectively reduce the economic cost by 27.3% compared with the benchmark algorithm.

aviation fuel nozzle, atomization characteristics, volume of fluid (vof), orthogonal experiment, sauter mean diameter (smd), structure optimization, Engineering (General). Civil engineering (General), TA1-2040, Chemical engineering, TP155-156, Naval architecture. Shipbuilding. Marine engineering, and VM1-989

Fuel atomization plays an important role in premixed combustion of aero-engine. In order to improve the atomization characteristics of an aviation fuel nozzle and optimize its structural parameters, the volume of fluid (VOF) interface capture algorithm and orthogonal experimental design were used to study the influence of internal flow and structural parameters (expansion angle, length of straight section, rise angle of swirl groove, and number of swirl groove) on the atomization characteristics. The results show that the local vortex on the swirl groove affects the fuel flow in the nozzle, and the local pressure loss can be eliminated by changing the structure of the swirl groove inlet. The number of swirl grooves has the most significant effect on Sauter mean diameter (SMD), the expansion angle is the biggest factor affecting the atomization cone angle, there is an optimal swirl groove elevation angle to minimize the oil film thickness, and the length of straight section has relatively little effect on the atomization characteristics. When the expansion angle is 60°, the length of straight section is 0.25 mm, the rising angle of swirl groove is 45°, the number of swirl grooves is 2, and the optimization effect is the best. After optimization, the oil film thickness decreases by 43.68%, the atomization cone angle increases by 3.70%, and the SMD decreases by 14.79%.

pollution index, water quality index, river pollution, water quality status, aceh watershed, Chemical engineering, and TP155-156

The rapid development of industrialization and urbanization in the world impact increased water pollution. Human activities, such as dam constructions, excessive water consumption, severance of river flows, compaction of riverbanks, and excessive use of riverbed vegetation, disrupt river flow and alter the original hydrological cycle. In response to these conditions, this study aims to analyze water quality and river quality status to set up a watershed environmental management strategy in Aceh Province as a case study. River water quality was analyzed descriptively by comparing the results of laboratory tests with parameters, namely TSS, pH, BOD, COD, DO, total phosphate, nitrate, and fecal coli. These parameters were then transformed into the environmental index (Water Quality Index and Pollution Index). It was found that Water Quality Index (WQI) results are shown from 50 to 70. WQI with the Good category is at Kr. Weh which is in the Central Aceh city. The medium-less type is found in 10 watersheds. The water quality with the category of Less is found at 3 points, namely Kr. Aceh, Cr. Doy, and Cr. Daroy. The quality of the river water in the Aceh region, from upstream to downstream, has decreased in quality with a lightly polluted status based on the Minister of Environment and Forestry of the Republic of Indonesia No. 27 of 2021 for class II.

molasses, lactic acid, lactobacillus acidophilus, fermentation, Chemical engineering, and TP155-156

Lactic acid is a chemical with widespread applications, mainly in pharmaceutical, cosmetic, chemical as well as food industries. One of the major uses of lactic acid is the polylactic acid (PLA) feedstock which is biodegradable and biocompatible as an alternative to plastic derived from fossil fuels. Efforts continue to be made to reduce the cost of producing PLA in order to compete with the conventional petrochemical-based plastics. This include the use of molasses as a raw material because it is cheap and contains high glucose. The purpose of this study was to obtain cell concentrations through the addition of starter volume that produces high concentrations of lactic acid and to obtain the growth kinetics of Lactobacillus acidophilus during the fermentation process. This study was conducted in several stages; the design of bioreactors, inoculation of Lactobacillus acidophilus, and fermentation of molasses. In a batch system, molasses substrate was directly inserted as much as 500 ml in the fermentor and the addition of starter volume of Lactobacillus acidophilus was 1; 3; 5 dan 10% v/v. The fermentation of molasses for 72 hours and the product was analysed every 8 hours. The highest concentration of lactic acid produced in batch fermented molasses was added to 5% (v/v) starter volume with 72 hours of fermentation time, which was 23.1 mg/L, with value the carrying-capacity coefficient (k) and the maximum net specific growth rate (µnet) were 0.2379 h-1 and 0.0160 h-1 respectively.

bioplastic, al2o3, starch, sago hampas, Chemical engineering, and TP155-156

Sago hampas are a waste with a high starch content. The starch from sago hampas can be used as a raw material for bioplastics. However, because bioplastics have a lower heat resistance than conventional plastics, additives are required to increase heat resistance. Aluminum oxide can be used as a metal compound that acts as an additive to increase heat resistance. Bioplastics were created using a weight percentage of 0, 1, 3, and 5% Al2O3. DTA was used to determine the melting point of bioplastics, as well as their mechanical properties, density, and water resistance. The best results were identified using FTIR and SEM. The results showed that adding Al2O3 at 1, 3, and 5% increased the heat resistance of bioplastics with melting points of 270, 274, and 280 oC. Except for mechanical properties, the best results were obtained with a melting point of 280 oC, tensile strength of 3.41 Mpa, elongation of 38.66%, density of 5.52 g cm-3, and 80.28% water resistance for bioplastics with 5% Al2O3 that suitable on Indonesian National Standard 7188.7:2016. The FTIR analysis revealed that bioplastics containing Al2O3 experienced physical interactions. Morphological analysis revealed that Al2O3 was evenly distributed on the bioplastic's surface.

amla seed oil, solvent extraction, phenol and flavonoid compounds, functional group, fatty acid components, Chemical engineering, and TP155-156

The results showed that the highest yield was obtained, namely 10.97% in the treatment of the raw material to solvent ratio of 1:30 and the extraction time of 120 minutes, while the lowest yield was 2.66% in the treatment of the raw material to solvent ratio of 1:20 and the extraction time of 30 minutes. Based on the phytochemical analysis, the highest concentrations of phenolic compounds and flavonoids, namely 66.12 mg GAE/g and 95.70 mg QE/g, were obtained from the treatment of the ratio of raw materials to solvents of 1:25 and extraction time of 120 minutes. Meanwhile, the lowest concentrations of phenol and flavonoids, namely 24.87 mg GAE/g and 39 mg QE/g, were achieved in the treatment of the raw material to solvent ratio of 1:20 and the extraction time of 30 minutes. The FTIR of amla seed oil with different aw material to solvent ratio and extraction times indicated the presence of the same functional group content. In the form of O-H indicating the presence of polyphenolic compounds, C=O indicating the presence of ascorbic acid compounds, C-O indicating the presence of pectin compounds, and C-O-C indicating flavonoid compounds in amla seed oil. The fatty acid components contained in amla seed oil analyzed using GCMS showed that the content of unsaturated fatty acids was higher than saturated fatty acids with linoleic acid as the main component. Physical-chemical analysis of pH, density, acid number, FFA, and peroxide number showed that the extracted oil quality was better than in previous studies.

aurivillius, srbi4ti4o15, photocatalyst material, degradation methylene blue, Chemical engineering, and TP155-156

The four-layered Aurivillius SrBi4Ti4O15 compound has been reported to be potentially used as a photocatalyst material. In this research, SrBi4Ti4O15 was prepared by the molten salt method using NaCl/KCl and then used to degrade methylene blue. The analysis of sample diffractogram indicated that the SrBi4Ti4O15 was obtained but there was still the impurities of Bi4Ti3O12. The micrograph showed that particle shape of SrBi4Ti4O15 is plate-like (sheets) with a lot of agglomeration. The band gap energy of SrBi4Ti4O15 is 3.14 eV (394.85 nm), according to the Kubelka-Munk calculation from the spectrum of reflectance. The photocatalytic test results showed that SrBi4Ti4O15 degraded methylene blue to 47.8% in 120 minutes.

red palm oil, fermentation, lactic acid bacteria, microencapsulation, Chemical engineering, and TP155-156

Red Palm Oil (RPO) is the result of refining from Crude Palm Oil (CPO) which still maintains a high level of phytonutrients that are beneficial for health. The benefits of RPO can be used as a nutraceutical source, because RPO acts as a provitamin A and vitamin E. The addition of Lactic Acid Bacteria (LAB) in a product functions as a probiotic with metabolite activity that can inhibit pathogenic microorganism thereby increasing the durability of a product. The addition of LAB to RPO is expected to increase the nutraceutical value by adding probiotic properties to RPO products. Microencapsulation technology can protect the bioactive content of essential oils against unwanted chemical interactions with other components and provide increased stability during processing. This research is expected to be able to provide information about the potential raw material of fermented RPO as a nutraceutical source by showing the profile of RPO before and after the fermentation process, chemical and physical properties of the microencapsulant. The microencapsulation technique used is the extrusion method. Fermentation of the bioactive compound ingredients in RPO using L. casei has a significant effect. RPO after fermentation using L. casei (Red-PalmZym) produces major compounds in the form of 9-Octadecenoic acid, methyl ester, (E)- Fermentation of RPO with L. casei increases the components of chemical compounds contained therein. The stability of the RPO microencapsulated before fermentation provided an effective protection against oxidative damage to the oil and proved that the microencapsulation process can reduce the level of damage to the oil.